In general, an exhaust gas filter refers to an exhaust gas after-treatment device to remove environmentally harmful substances from exhaust gas exhausted from an engine of a vehicle. Particularly, a diesel engine generates a large amount of fine dust due to nitrogen oxides and oxidation of carbon, as compared to a gasoline engine, and various devices to remove such dust are provided.
Particularly, in a diesel engine, foreign substances having fine particles, such as fine dust, generate smoke and are internationally subject to regulations. Therefore, an exhaust gas filter to remove such fine dust may be provided and, as a usage period of the exhaust gas filter increases, the amount of foreign substances collected in the filter increases and lowers the performance of the filter.
In order to solve lowering of the performance of the filter, a method of regenerating a filter by removing foreign substances having fine particles collected in the filter using exhaust gas of a high temperature generated when an engine is operated at a high RPM is used. In addition, many enterprises have tried to develop filter regeneration methods.
In connection with the above method, reference may be made to Korean Patent Registration No. 10-0398151 entitled “Auxiliary air supplying device for improving DPF purification rate and purification method”.
However, in the method for regenerating a filter by removing foreign substances having fine particles collected in the filter using exhaust gas of a high temperature generated when an engine is rotated at a high RPM, if the engine returns to a low RPM after regeneration of the filter has been completed, the amount of exhaust gas decreases, engine cooling effects are reduced, and the concentration of oxygen in the exhaust gas increases and reacts with remaining fuel in an exhaust pipe, thus continuously increasing the temperature of the exhaust gas and causing heat damage to the filter.
The above description has been made only for a better understanding of the background of the disclosure but it is understood by those skilled in the art that it corresponds to known technology.